Design method of memory alloy pipe connector based on radial shrinkage stress model

Abstract

The present invention relates to the technical field of memory alloy pipeline connectors, and discloses a design method for memory alloy pipeline connectors based on a radial contraction stress model. The method first obtains the contraction gap T and contraction stress σ of the memory alloy pipeline connector when a typical pipe diameter is connected, and draws a contraction gap-stress curve diagram; then an open downward parabola curve and a decreasing logarithmic curve are used to fit the contraction gap-stress curve diagram, and a radial contraction stress equation of the memory alloy pipeline connector is established; finally, based on the radial contraction stress equation of the memory alloy pipeline connector, the maximum contraction stress, maximum contraction gap and minimum contraction gap of the memory alloy pipeline connector when a typical pipe diameter is connected are obtained, and then the maximum contraction stress, maximum contraction gap and minimum contraction gap of the corresponding memory alloy pipeline connector when any pipe diameter is connected are calculated. The present invention can scientifically guide the design of radial contraction stress and contraction gap of the memory alloy pipeline connector, and improve the design efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of pipeline connection, in particular to a shape memory alloy pipeline connector, and more specifically to a design method of a shape memory alloy pipeline connector based on a radial contraction stress model. Background Art

[0002] With the in-depth research and process application of shape memory alloy materials, industries such as aviation, aerospace, and precision electronics have gradually begun to make full use of the "heating and shrinking" recovery effect of shape memory alloy materials, making the inner diameter of the shape memory alloy pipeline connector shrink and become smaller. The generated radial contraction stress directly acts on the outer wall of the connected pipe, realizing the sealed connection between the two pipes, and having the characteristics of simple and reliable connection methods.

[0003] In order to facilitate the insertion of the connected pipe, there is a certain gap (hereinafter referred to as the shrinkage gap T) between the shape memory alloy pipeline connector and the outer diameter of the pipe before heating and shrinking. After the shape memory alloy pipeline connector is heated and shrunk, there are usually the following three situations, as Figure 2 shown:

[0004] 1) Connection gap area: When the shrinkage gap T of the shape memory alloy pipeline connector is greater than Tmax, that is, the inner diameter of the shape memory alloy pipeline connector is greater than the outer diameter of the pipe after heating and shrinking, no shrinkage stress is generated on the outer wall of the pipe, and the connection fails. This gap is the maximum shrinkage gap Tmax.

[0005] 2) Connection effective area: When the shrinkage gap of the shape memory alloy pipeline connector satisfies Tmin < T < Tmax, the inner diameter of the shape memory alloy pipeline connector is smaller than the outer diameter of the pipe after heating and shrinking, and a certain shrinkage stress is generated on the outer wall of the pipe. However, the shrinkage stress is not sufficient to collapse the pipe, and the effective connection of the pipe can be realized. When the gap is Tmin, the shrinkage stress is the largest, reaching the maximum value σmax, which is less than the tensile strength of the shape memory alloy material and greater than the yield strength of the pipe material, that is, σs < σmax > σ b , which is called the optimal connection. This gap is the minimum shrinkage gap Tmin.

[0006] 3) Connection collapse area: When the shrinkage gap T of the shape memory alloy pipeline connector is less than Tmin, the inner diameter of the shape memory alloy pipeline connector is smaller than the outer diameter of the pipe after heating and shrinking, and the shrinkage stress generated on the outer wall of the pipe is sufficient to collapse the pipe, and the connection fails.

[0007] Therefore, under the condition of a certain outer diameter of the pipe, determining the minimum connection gap Tmin of the memory alloy pipeline connector can ensure the best connection between the memory alloy and the pipe. However, in actual engineering applications, there is no mature test method for the minimum connection gap Tmin. More often, a gap value is assumed, and a connection test is performed to determine whether the connection part is leaking. Through repeated process tests, the sealing and connection strength after connection can meet the requirements. As for whether it is the best connection, it is not considered too much. As for the maximum shrinkage gap Tmax, it is necessary to conduct multiple experiments to infinitely approximate it, which is rarely used in process applications.

[0008] The invention patent with publication number CN103698073A discloses a shape memory alloy pipe joint tightening pressure test device and its test method. The strain gauge is attached to the inner wall of the pipe, and the tightening force generated by the pipe during the heating recovery process can be measured. This test method actually measures the torsional force between the pipe joint and the pipe being taken, not the tightening force generated by the pipe joint on the pipe being taken. There is a friction coefficient relationship between the tightening force and the torsional force. At the same time, the strain gauge is attached to the inner wall of the pipe, while the torsional force actually acts on the outer wall of the pipe. There is a wall thickness in the middle, and there is a difference between the inner diameter deformation and the outer diameter deformation. The strain obtained cannot truly reflect the external deformation, and there is an error in the measurement result.

[0009] For another example, the invention patent with publication number CN112697834A discloses a shape memory alloy restoring force performance testing method and testing system, which measures the temperature and restoring force values ​​of the shape memory alloy rod in the axial direction, but is not suitable for measuring the shrinkage stress of pipeline connectors.

[0010] Furthermore, the two articles "Simulation Calculation of Radial Compressive Stress of TiNiNb Shape Memory Alloy Pipe Joints" and "Simulation of Stress Field of TiNiFe Shape Memory Alloy Pipe Joints" analyzed the stress of the TiNiNb pipe joint connection process through elastic-plastic theory and established a mechanical model. The former simulated the change of radial compressive stress with temperature based on the model; the latter studied the influence of parameters such as the inner diameter, wall thickness and assembly clearance of the pipe joint on the radial compressive stress.

[0011] The article "Modeling and Simulation Research on the Whole Process of NiTiFe Shape Memory Alloy Pipe Joint Connection" established a finite element model of the whole process of connection such as contact and clamping of TA18 high-strength titanium pipe of specific specifications based on the thermodynamic parameters of the shape memory alloy material, and obtained the optimal structural parameters of the pipe joint.

[0012] The mechanical model construction method and finite element analysis method in the above articles inevitably have problems such as mechanical model simplification and boundary condition simplification when constructing stress fields. Therefore, they can only guide the rules in actual industrial applications but cannot be used to determine specific values. At the same time, for memory alloy pipes of different specifications and diameters, relevant basic tests need to be carried out separately, and the material data model and boundary data conditions need to be constructed and then the above methods can be repeated to obtain the shrinkage stress of different diameters. Summary of the invention

[0013] In order to solve the problems and shortcomings existing in the above-mentioned prior art, the present invention proposes a design method for memory alloy pipe connectors based on a radial shrinkage stress model. The present invention comprehensively considers the deformation behavior of the memory alloy under complex thermodynamic environments and complex loading conditions of multiple processes, and constructs a radial shrinkage stress model for memory alloy pipe connectors with different pipe diameters and different gaps. Based on the radial shrinkage stress model, the design process of radial shrinkage stress and shrinkage gap of the memory alloy pipe connector is scientifically guided, the design efficiency is improved, and it can be used in actual production.

[0014] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0015] The present invention provides a method for designing a memory alloy pipeline connector based on a radial shrinkage stress model, the method comprising the following steps:

[0016] The first step is to first obtain the shrinkage gap T and shrinkage stress σ of the memory alloy pipe connector used in typical pipe diameter connections, and then draw a shrinkage gap-stress curve.

[0017] In the present invention, the typical pipe diameter may be understood as the minimum pipe diameter D1, the middle pipe diameter D2 and the maximum pipe diameter D3 that may appear in the connecting pipe during the actual processing.

[0018] In the present invention, the shrinkage gap T of the memory alloy pipe connector used for typical pipe diameter connection is generally determined according to the material shrinkage performance of the memory alloy itself, and is generally between 0.01 and 0.3. If the shrinkage performance is small, a small value is taken, and if the shrinkage performance is large, a large value is taken.

[0019] In the present invention, the shrinkage gap-stress curve of a typical pipe diameter is determined by at least 5 data measurement points (such as P11, P12, ..., P15) on the memory alloy pipe connector, and the curve has at least 1 data measurement point (such as P11) in the connection collapse area (Type III) and at least 4 data measurement points (such as P12, ..., P15) in the connection effective area (Type II). A set of shrinkage stress measurement test pieces needs to be set at each data measurement point. After the memory alloy pipe connector shrinks, the pipe is compressed, and the shrinkage stress σ is directly measured by the stress strain gauge attached to the data measurement point, such as Figure 4 The corresponding shrinkage stress σ of the data measurement point on the memory alloy pipe connector is measured by the following steps:

[0020] Step 1. First determine the minimum outer diameter D1, the middle outer diameter D2 and the maximum outer diameter D3 of the connected pipeline;

[0021] Step 2. Determine the shrinkage gap T at the corresponding data measurement point of the memory alloy pipe connector when connecting the above pipes with different diameters;

[0022] Step 3. Determine the inner diameter M of the corresponding memory alloy pipe connector when connecting the pipes with the minimum outer diameter D1, the median outer diameter D2 and the maximum outer diameter D3;

[0023] Step 4. Heat the memory alloy pipe connector to shrink the memory alloy pipe connector and compress the pipe. The stress strain gauge at the data measurement point measures the corresponding shrinkage stress σ.

[0024] Finally, based on the shrinkage gap T and shrinkage stress σ obtained at the data measurement points at the memory alloy pipe connector when connecting pipes with different diameters, a shrinkage gap-stress curve is drawn.

[0025] In the present invention, when different typical pipe diameters are connected, the inner diameter M of the corresponding memory alloy pipe connector is as follows: when the minimum outer diameter (D1) pipe is connected, the corresponding inner diameter of the memory alloy pipe connector is D1+2*Tn (n=1~5), Tn is the shrinkage gap; when the intermediate outer diameter (D2) pipe is connected, the corresponding inner diameter of the memory alloy pipe connector is D2+2*Tn (n=1~5). When the maximum outer diameter (D3) pipe is connected, the corresponding inner diameter of the memory alloy pipe connector is D3+2*Tn (n=1~5). On this basis, the processing of the memory alloy pipe connector is completed based on the calculated inner diameter value, and actual measurement is performed, and the measured value is used instead of the theoretical value.

[0026] The second step is to fit the obtained shrinkage gap-stress curve using an open downward parabolic curve and a decreasing logarithmic curve, and then obtain the corresponding radial shrinkage stress equation of the memory alloy pipe connector. The maximum shrinkage stress, maximum shrinkage gap and minimum shrinkage gap of the memory alloy pipe connector when connecting a typical pipe diameter are obtained through the equation.

[0027] In the present invention, since the data measurement points are distributed in the connection collapse area (Type III) and the connection effective area (Type II) of the memory alloy pipe connector, the shrinkage gap-stress curve drawn is generally two segments, so when fitting, different methods need to be used to fit the two segments of the curve. The following takes the minimum pipe diameter as an example for explanation:

[0028] The three points (P11, P12, and P13) with the smallest shrinkage gap measured when connecting with the minimum pipe diameter (D1) are fitted with the open downward parabola curve equation to obtain the following radial shrinkage stress equation for the memory alloy pipe connector:

[0029] (1);

[0030] Among them, T1min is the minimum shrinkage gap of the memory alloy pipe connector corresponding to the minimum pipe diameter (D1); σ1max is the maximum shrinkage stress of the memory alloy pipe connector corresponding to the minimum pipe diameter (D1);

[0031] Furthermore, the three points (P13, P14, and P15) with the largest shrinkage gap measured when the minimum pipe diameter (D1) is connected are used to fit the curve using a decreasing logarithmic curve equation, and the following radial shrinkage stress equation of the memory alloy pipe connector is obtained:

[0032] (2);

[0033] Then, the maximum shrinkage gap T1max of the memory alloy pipe connector can be inferred from formula (2). The inverse formula is as follows:

[0034] .

[0035] Using the same method as above, the maximum shrinkage stress σ2max, minimum shrinkage gap T2min, and maximum shrinkage gap T2max of the memory alloy pipe connector corresponding to the intermediate pipe diameter (D2); and the maximum shrinkage stress σ3max, minimum shrinkage gap T3min, and maximum shrinkage gap T3max of the memory alloy pipe connector corresponding to the maximum pipe diameter (D3) can be calculated.

[0036] The third step is to calculate the maximum shrinkage stress, maximum shrinkage gap and minimum shrinkage gap of the memory alloy pipe connector when connecting with any pipe diameter according to the maximum shrinkage stress, maximum shrinkage gap and minimum shrinkage gap of the memory alloy pipe connector when connecting with typical pipe diameters, and then design and manufacture the corresponding memory alloy pipe connector according to the maximum shrinkage gap and minimum shrinkage gap.

[0037] In the present invention, after obtaining the maximum shrinkage stress, maximum shrinkage gap and minimum shrinkage gap of the memory alloy pipeline connector corresponding to the typical pipe diameter connection by the above method, the maximum shrinkage stress, maximum shrinkage gap and minimum shrinkage gap of the memory alloy pipeline connector corresponding to the arbitrary pipe diameter connection can be calculated by arc interpolation or linear interpolation, and then the inner diameter value range D+2*Tmin≤M≤=D+2*Tmax of the memory alloy pipeline connector is calculated based on the obtained maximum shrinkage gap and minimum shrinkage gap. When designing and manufacturing the memory alloy pipeline connector, its inner diameter specification within the above range can ensure the reliable connection of the pipeline.

[0038] In the present invention, the maximum contraction stress of the memory alloy pipeline connector should be less than the tensile strength σb of the memory alloy material and greater than the yield strength σs of the material of the connected pipeline.

[0039] Beneficial effects of the present invention:

[0040] (1) The present invention innovatively proposes a radial shrinkage stress model for memory alloy pipe connectors. Based on the radial shrinkage stress model, the design process of radial shrinkage stress and shrinkage gap of memory alloy pipe connectors is scientifically guided, thereby improving the design efficiency.

[0041] (2) The method of the present invention can construct a radial shrinkage stress model of memory alloy pipeline connectors with different pipe diameters and different gaps. The established stress model is scientific and accurate, and the maximum shrinkage stress state and the minimum shrinkage gap can be determined through the model, thereby achieving high-reliability connection of the pipeline, reducing the number of traditional repeated process tests, and having low comprehensive costs and high economic benefits.

[0042] (3) The present invention replaces the traditional trial and error method with scientific test experiments, accurately determines the maximum shrinkage stress and the minimum shrinkage gap, reduces the process development cost, shortens the cycle and increases efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The foregoing and following detailed description of the present invention will become more apparent when read in conjunction with the following drawings, in which:

[0044] Figure 1 This is a schematic diagram of the memory alloy pipeline connection of the present invention;

[0045] Figure 2 This is a schematic diagram of the memory alloy pipeline connector of the present invention after heating and shrinkage;

[0046] Figure 3 It is the radial shrinkage stress model of the memory alloy pipeline connector of the present invention;

[0047] Figure 4 This is a schematic diagram of a radial shrinkage stress measurement test piece of the present invention.

[0048] In the figure:

[0049] 1. Memory alloy pipe connector; 2. Connected pipe; 3. Stress strain gauge; 4. Stress strain signal line. DETAILED DESCRIPTION

[0050] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions for achieving the purpose of the present invention will be further described below through several specific embodiments. It should be noted that the technical solutions claimed for protection in the present invention include but are not limited to the following embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work shall fall within the scope of protection of the present invention.

[0051] With the in-depth research and process application of shape memory alloy materials, the aviation, aerospace, precision electronics and other industries have gradually begun to make full use of the "heating and shrinkage" recovery effect of shape memory alloy materials, so that the inner diameter of the shape memory alloy pipe connector shrinks and becomes smaller. The radial shrinkage stress generated directly acts on the outer wall of the connected pipe, realizing a sealed connection between the two pipes, which has the characteristics of simple and reliable connection.

[0052] In order to facilitate the insertion of the connected pipe, there is a certain gap between the memory alloy pipe connector and the outer diameter of the pipe before heating and shrinking (hereinafter referred to as the shrinkage gap T). Under the condition of a certain outer diameter of the pipe, determining the minimum connection gap Tmin of the memory alloy pipe connector can ensure the best connection between the memory alloy and the pipe. However, in actual engineering applications, there is no mature test method for the minimum connection gap Tmin. More often, a gap value is assumed, and a connection test is performed to determine whether the connection part is leaking. Through repeated process tests, the sealing and connection strength after connection can meet the requirements. As for whether it is the best connection, it is not considered too much. As for the maximum shrinkage gap Tmax, it is necessary to conduct multiple experiments to approach it infinitely, which is rarely used in process applications.

[0053] Based on this, an embodiment of the present invention proposes a design method for a memory alloy pipe connector based on a radial shrinkage stress model. The present invention innovatively proposes a radial shrinkage stress model for a memory alloy pipe connector. Based on the radial shrinkage stress model, the design process of the radial shrinkage stress and shrinkage gap of the memory alloy pipe connector is scientifically guided, thereby improving the design efficiency.

[0054] The present invention is further explained and illustrated below through specific application schemes.

[0055] In this embodiment, the connected pipeline is 1Cr18Ni9Ti pipe, whose yield strength σs=225Mpa, the minimum outer diameter D1 of the pipeline is 10mm, the maximum outer diameter D3=60mm, and the memory alloy pipeline connector used is made of NiTiNb memory alloy, with a tensile strength σb=850MPa. Figure 1 At present, it is necessary to determine the minimum shrinkage gap Tnmin and the maximum shrinkage stress σnmax of the NiTiNb memory alloy pipeline connector used when connecting a pipeline with an outer diameter Dn=45mm.

[0056] The first link:

[0057] Step 1: According to the actual situation, determine the minimum pipe diameter D1=10, the middle pipe diameter D2=30, and the maximum pipe diameter D3=60 of the connected pipe.

[0058] Step 2: Determine the shrinkage gaps T1~T5 of the five data measurement points on the shrinkage gap-stress curve. The actual selections are T1=0.04, T2=0.07, T3=0.10, T4=0.15, and T5=0.25.

[0059] Step 3: After calculation, the inner diameters of the five memory alloy pipe connectors with the smallest pipe diameter (D1) are 10.08, 10.14, 10.2, 10.3, and 10.5 respectively; the inner diameters of the five memory alloy pipe connectors with the intermediate pipe diameter (D2) are 30.08, 30.14, 30.2, 30.3, and 30.5 respectively; the inner diameters of the five memory alloy pipe connectors with the largest pipe diameter (D3) are 60.08, 60.14, 60.2, 60.3, and 60.5 respectively. On this basis, the processing of the above-mentioned memory alloy pipe connectors is completed.

[0060] After the processing is completed, the two pipes are butt-connected using a memory alloy pipe connector, and a stress strain gauge is pasted at the data measurement point of the memory alloy pipe connector. The data of the stress strain gauge is exported through the stress strain signal line connected to it. Then the memory alloy pipe connector is heated to shrink the memory alloy pipe connector and press the pipe, and the corresponding shrinkage stress σ of the memory alloy pipe connector at the data measurement point is read. Finally, according to the shrinkage gap and shrinkage stress obtained at the data measurement point of the memory alloy pipe connector, the corresponding shrinkage gap-stress curve is drawn, such as Figure 3 shown.

[0061] The second part:

[0062] Use the three data measurement points (P11, P12, P13) with the smallest shrinkage gap on the smallest pipe diameter (D1) and adopt the open downward parabolic curve equation ( )Fit the corresponding curve and calculate the corresponding parameters a=-150792, T1min=0.054, σ1max=810.35;

[0063] Use the three data measurement points (P13, P14, P15) with the largest shrinkage gap on the smallest pipe diameter (D1) and use the decreasing logarithmic curve equation ( )Fit the corresponding curve and calculate the corresponding parameters p=-230.13, q=4.62, w=0.0744;

[0064] Then by the formula , the maximum shrinkage gap T1max=0.291 of the memory alloy pipe connector with the minimum pipe diameter (D1) is calculated.

[0065] Using the same method, the parabolic curve parameters a=-262827, T2min=0.061, σ2max=750.05 and logarithmic curve parameters p=-121.47, q= 4.51, w= 0.0876 of the intermediate pipe diameter (D2) can be calculated, and the maximum shrinkage gap T2max= 0.31 of the memory alloy pipe connector corresponding to the intermediate pipe diameter (D2) can be calculated.

[0066] Using the same method, the parabolic curve parameters a= -348829, T3min=0.068, σ3max= 656.67 and logarithmic curve parameters p=-71.6, q=4.36, w=0.0965 of the maximum pipe diameter (D3) can be calculated, and the maximum shrinkage gap T3max=0.326 of the memory alloy pipe connector corresponding to the maximum pipe diameter (D3) can be calculated.

[0067] The third link:

[0068] Using the maximum shrinkage stress σ1max of the smallest pipe diameter (D1), the maximum shrinkage stress σ2max of the middle pipe diameter (D2) and the maximum shrinkage stress σ3max of the largest pipe diameter (D3) to form three points, arc interpolation is used to calculate the maximum shrinkage stress σnmax=704.09 of the memory alloy pipe connector when connecting a pipe with an outer diameter of 45mm. In the same way, the minimum shrinkage gap Tnmin=0.0654 and the maximum shrinkage gap Tnmax=0.321 are calculated.

[0069] Check that the maximum shrinkage stress (σ1max, ..., σnmax) should be less than the tensile strength σb = 850MPa of NiTiNb memory alloy, which meets the requirements. Check that the maximum shrinkage stress (σ1max, ..., σnmax) should be greater than the yield strength σs = 225MPa of 1Cr18Ni9Ti pipe, which meets the requirements. Therefore, when connecting a pipeline with an outer diameter of 45mm, the minimum shrinkage gap Tnmin = 0.321mm and the maximum shrinkage stress σnmax = 704.09MPa of the NiTiNb memory alloy pipeline connector can be used for actual product processing to ensure the most reliable connection and the best sealing.

[0070] In the description of the present invention, it is necessary to understand that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as an obstacle to the scope of protection of the present invention.

[0071] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "setting", "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0072] The above description is only a preferred embodiment of the present invention and does not constitute any form of hindrance to the present invention. Any simple modification or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A design method for a memory alloy pipeline connector based on a radial shrinkage stress model, characterized in that: include: Obtain the shrinkage gap T and shrinkage stress σ of the memory alloy pipe connector corresponding to the typical pipe diameter connection, draw a shrinkage gap-stress curve, and the resulting shrinkage gap-stress curve is divided into two sections; The two curves are fitted in different ways, wherein the data of the three data measurement points with the smallest shrinkage gap are selected, and the shrinkage gap-stress curve is fitted with an open downward parabola curve to establish the radial shrinkage stress equation of the memory alloy pipe connector; and, The data of the three measurement points with the largest shrinkage gap are selected, and the shrinkage gap-stress curve is fitted with a decreasing logarithmic curve to establish the radial shrinkage stress equation of the memory alloy pipe connector; Based on the radial shrinkage stress equation of memory alloy pipe connectors, the maximum shrinkage stress, maximum shrinkage gap and minimum shrinkage gap of the memory alloy pipe connectors when connecting typical pipe diameters are obtained, and then the maximum shrinkage stress, maximum shrinkage gap and minimum shrinkage gap of the corresponding memory alloy pipe connectors when connecting any pipe diameter are calculated.

2. The method for designing a memory alloy pipeline connector based on a radial shrinkage stress model according to claim 1, characterized in that: When connecting typical pipe diameters, at least five data measurement points of the memory alloy pipe connector are collected for shrinkage clearance T and shrinkage stress σ, wherein the connection collapse area of ​​the memory alloy pipe connector has at least one data measurement point and the connection effective area has at least four measurement points.

3. The method for designing a memory alloy pipeline connector based on a radial shrinkage stress model according to claim 1, characterized in that: The shrinkage gap T and shrinkage stress σ of the memory alloy pipe connector corresponding to the typical pipe diameter connection are obtained, and the shrinkage gap-stress curve is drawn, as follows: Step 1. Determine the minimum outer diameter D1, median outer diameter D2 and maximum outer diameter D3 of the connected pipeline; Step 2. Determine the shrinkage gap at the data measurement point of the memory alloy pipe connector corresponding to the connection of different pipe diameters; Step 3. Determine the inner diameter M of the corresponding memory alloy pipe connector when connecting the pipes with the minimum outer diameter D1, the median outer diameter D2 and the maximum outer diameter D3; Step 4. Heat the memory alloy pipe connector to shrink the memory alloy pipe connector and then press the pipe, and measure the corresponding shrinkage stress σ of the memory alloy pipe connector at the data measurement point; Step 5. Based on the shrinkage gap and shrinkage stress obtained at the data measurement points at the memory alloy pipe connector when connecting pipes of different diameters, draw a shrinkage gap-stress curve.

4. The method for designing a memory alloy pipeline connector based on a radial shrinkage stress model according to claim 1, characterized in that: The shrinkage gap-stress curve is fitted with an open downward parabola curve to establish the radial shrinkage stress equation of the memory alloy pipe connector. The equation expression is as follows: （1）； Among them, Tmin is the minimum shrinkage gap; σmax is the maximum shrinkage stress.

5. The method for designing a memory alloy pipeline connector based on a radial shrinkage stress model according to claim 1, characterized in that: The shrinkage gap-stress curve is fitted using a decreasing logarithmic curve to establish the radial shrinkage stress equation of the memory alloy pipe connector. The equation is as follows: （2）。 6. The method for designing a memory alloy pipeline connector based on a radial shrinkage stress model according to claim 1, characterized in that: According to the maximum shrinkage stress, maximum shrinkage gap and minimum shrinkage gap of the memory alloy pipe connector when connecting a typical pipe diameter, the maximum shrinkage stress, maximum shrinkage gap and minimum shrinkage gap of the corresponding memory alloy pipe connector when connecting an arbitrary pipe diameter are calculated by interpolation.

7. The method for designing a memory alloy pipeline connector based on a radial shrinkage stress model according to claim 1, characterized in that: The maximum shrinkage stress of the memory alloy pipe connector should be less than the tensile strength of the memory alloy material and greater than the yield strength of the material of the connected pipe.

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